A single dose of vitamin D might bolster the ability of the immune system to prevent the development of active tuberculosis for six weeks or more among people who have been exposed to Mycobacterium tuberculosis, the bacteria that causes TB, according to a study recently published in the American Journal of Respiratory and Critical Care Medicine, the PA/Irish Examiner reports.

Adrian Martineau of the Imperial College London and colleagues from Queen Mary's School of Medicine and Dentistry and the Wellcome Trust Center for Research conducted the study among about 200 people who had been exposed to M. tuberculosis. Approximately two thirds of the study participants had latent TB, while the rest had not been infected with the bacteria, the researchers found.

Researchers took blood from all study participants and infected the samples with M. tuberculosis. They then split the participants into two groups. The first group was given a placebo, and the other group was given a 2.5 mg dose of vitamin D. After six weeks, researchers took additional blood samples and infected them with M. tuberculosis. After 24 hours, the samples were analyzed, and the researchers found the samples taken from the group that had taken the vitamin D pills showed 20% less growth than the group that had taken the placebo.

The scientists also found that more than 90% of study participants had a vitamin D deficiency but that the supplement helped boost the immune system's ability to fight infection. 'We found that a single large dose of vitamin D was sufficient to enhance a person's immunity to the bacteria,' Martineau said, adding, 'This is very significant given the high levels of vitamin D deficiency in people at the highest risk of TB infection and shows that a simple, cheap supplement could make a significant impact on the health of people most at risk from the disease'.

Chris Griffiths from Queen Mary's said that identifying people with latent TB and providing them with vitamin D supplements 'could be an important strategy for tackling the disease'.

Vitamin D was used to treat TB in sanatoriums before antibiotics were used, according to BBC News. Peter Davies, a chest specialist and secretary of TB Alert, said it is positive that the study's findings confirmed what already was suspected about the benefits of vitamin D. 'What makes this a potentially very good intervention is that it is cheap and easy to administer,' he said, adding that additional clinical trials are needed to confirm the study's findings.